1. Field of the Invention
The present invention is directed to special-purpose sunglasses with lenses for use during flying a jet aircraft. These sunglasses reduce glare from high illumination in the far field of vision when viewing in the intermediate or near fields of vision. These lenses greatly improve the pilot's ability to see the instrument panel and make viewing between highly contrasting fields of vision less stressful to the eyes.
2. Prior Art
In the field of optical wear, a wide variety of sunglasses and goggles have been developed over the years for various purposes, depending upon the specific function of the sunglasses or the activity involved while wearing the sunglasses. Optical wear has been created to reduce glare from point sources of light, such as from oncoming cars or from direct sunlight. Optical wear has also been created to reduce the glare from broad regions of high illumination, such as office lighting, sky glare, and ground glare. Optical wear also has been developed for directing sight into specific fields of vision. This type of eyewear enables the viewer to assume a correct posture or position for carrying out a physical activity; the great majority of the prior art in this application has been in developing golfing glasses. Finally, optical wear has been designed to reduce visual stress in contrasting lighting situations and to enhance feature extraction in different fields of vision, these types of optical wear can be useful during physical activities where it is desirable to see a specific object against a background, such as golfing, fishing, hunting or other outdoor recreational activities.
One area that prior art has not addressed is the situation encountered by pilots of jet aircraft, which are flown typically at altitudes between 35,000 and 45,000 feet. At these heights during the day, the illumination from outside the cockpit is especially high. The high illumination comes from scattered light from both the sky and clouds. Indeed, when flying over clouds, pilots typically experience illumination values around 9,000 lux even when they are not looking in the direction of the sun. By contrast, under these external lighting conditions, the illumination of the instrument panel can be typically around 30 lux. In this case, the ratio between the outside illumination to that of the instrument panel is 300 to 1. Making transitions between these two contrasting fields of illumination can be stressful to the eyes.
Of the variations of sunglasses disclosed in prior art, none has satisfactorily solved the problem of balancing the illumination between outside and inside the cockpit—a problem that pilots flying at altitude encounter. Ordinary dark sunglasses do not solve this problem; while they do reduce the outside illumination to a comfortable level for the pilot, they can render the instrument panel too dark for the pilot to discern readings on the gauges. On the other hand, vignetted sunglass lenses assist in the overall balancing of illumination outside the cockpit with that of the instrument panel, but they permit too much light to enter a pilot's eyes, thus causing glare when the pilot views the instruments.
The limitations of prior art described above highlight the need for sunglasses that specifically address the two and often related problems that many jet pilots routinely encounter when flying at altitude: that is, (1) the contrast in illumination causes stress on the pilot's eyes resulting from the eyes having to adjust back and forth between the high illumination from outside the cockpit and the low illumination from the instrument panel; and (2) the glare caused by the high illumination can degrade the ability of the pilot to adequately see the instruments. Moreover, these two problems are exacerbated as the pilot ages.
To fully understand the problem the present invention solves, it is helpful to define the difference between the horizon and the horizontal plane in which the aircraft is flying. The horizon is plane tangent to the earth's surface at an observer's position and the horizontal plane is perpendicular to the vertical axis to the earth. Between 35,000 ft and 45,000 ft the horizon is approximately 3.3° to 3.8° below the horizontal plane. Consequently, whenever the aircraft is above a uniform layer of cloud that extends to the horizon, the illumination from that cloud layer originates from below the horizontal plane.
The illumination that a pilot experiences when flying at these high altitudes can be significantly different from that experienced by a person on the ground. For example, when pilots fly above the clouds, the illumination experienced when they look horizontally and below is typically greater than when they look above the horizontal plane. This high illumination at and below the horizontal plane poses a unique problem for pilots when they look at the instruments in that the high illumination from outside the cockpit can be relatively close to their intermediate field of vision of the instruments. The reverse tends to be the case for a person on the ground, where the illumination generally increases when looking upwards.
The lenses of the present invention, when adapted to sunglasses, enable a pilot to easily view outside the cockpit into high illumination and simultaneously view the instrument panel in low illumination without the eyes having to compensate for the previously described problems of adjustment and glare. This invention reduces visual stress to the eyes by greatly reducing the difference in illumination as received by the eyes between lighting outside the cockpit and the instrument panel. In addition, this reduction in light received by the eyes from outside the cockpit greatly reduces glare that can impair the pilot's vision of the instrument panel.
The present invention addresses the specific and unique condition present in the cockpit of a jet aircraft where the instrument panel and nose of the aircraft block the high illumination from outside the cockpit from entering the intermediate section of the lenses.
The following United States Patents are representative of the prior art and are incorporated herein by reference.
Kerns, Jr. et al. (U.S. Pat. No. 6,623,116) discloses eyeglass lenses with multiple optical zones having varying optical properties for enhanced visualization of different scenes in outdoor activities. The different optical zones in the lenses can be arranged in typical bi-focal fashion with an abrupt line transmission between an upper and lower zone. Alternatively, the second optical zone can be an oval or circle positioned in a specific location within the lens body. This patent does not disclose three distinct areas on the lens for far, intermediate and near vision, nor does this patent disclose glare reduction from light coming to the viewer from the far field of vision. In addition, this patent does not disclose the need to balance the light intensity between the different fields of vision.
Baiocchi, et al. (U.S. Pat. No. 5,975,695) discloses an optical element that balances the contrast between high and low illuminations and uses selected spectral transmittance for feature enhancement. Even though a particular embodiment states the patent is suitable for flying aircraft, this invention has vignetted lenses, which have high density tinting at the top of the lenses and transition to less density towards the lower portion of the lens. This patent is directed primarily to address two different fields of vision and does not disclose glare reduction. Unlike the present invention, this patent does not disclose non-vignetted lenses with a sharp (discontinuous) transition between the field of vision for viewing the sky and the field of vision for viewing the instrument panel. This patent also does not disclose three distinct areas on the lens for far, intermediate and near vision, nor does this patent disclose glare reduction from light coming to the viewer from the forward direction. In addition, this patent does not disclose the need to balance the light intensity between the different fields of regard.
In the Baiocchi patent, the ratio of transmittance between the lighter tinted portions of the lens to the darker tinted portion of the lens is between 1.5 to 7, preferably between 2.5 and 6.5. In the present invention, this ratio is between 4 and 64, preferably between 8 and 16. The present invention is made to be used in lighting situations that are highly contrasting.
Sherman, et al. (U.S. Pat. No. 5,682,220) discloses sunglasses that provide highlighted vision through a vision directing section so that the wearer's vision is directed to that portion of their field of vision. This patent does not disclose glare reduction, and these sunglasses can be worn anytime and anywhere a person would wear normal sunglasses. This patent does not balance the light from the far field, intermediate field and near field in order to enable the viewer to see equally well in all three fields of regard. This patent also does not disclose lenses to be used to reduce glare when a pilot views the instrument panel, when glare is caused by high illumination from outside the cockpit.
In the Sherman patent the far field of vision area of the lens has a range of transmittance between 53 and 30%. In the vision directing section of the lens the range in transmittance is between 75 and 50%. This patent is directed towards sunglasses that would be appropriately used in environments having normal brightness. These sunglasses are not designed for use in environments having high to exceptionally high brightness, where the present invention is intended for use.
In the Sherman patent, the ratio of the transmittances between the vision directed portion of the lens to the far field portion of the lens varies between 1.43 and 1.67. These are low values and indicate that the vision directed portion of the lens only highlights this region of viewing as compared to the far field of vision. Simply put, the vision directed portion of the lens just reminds the viewer where to look. These sunglasses will not enable the viewer to look into highly contrasted illuminated scenes. In the present invention, the ratio between the transmittance of the intermediate and far fields of vision is preferably between 4 and 16.
Gilson, et al. (U.S. Pat. No. 4,542,964) discloses eyewear to be worn primarily in the office environment to enable the viewer of a visual display terminal or monitor to comfortably view the monitor over extended periods of time. In this patent, the upper portion of the lenses is opaque and not intended permit viewing; in addition, the lenses are primarily intended to be used for intermediate viewing. This patent does not disclose three distinct areas on the lens for far, intermediate and near vision, nor does this patent disclose glare reduction from light coming to the viewer from the forward direction. In addition, this patent does not disclose the need to balance the light intensity between the different fields of regard.
Adrian, et al. (U.S. Pat. No. 4,338,003) discloses glasses used to mitigate glare primarily from point sources of light from oncoming headlights and in an office environment. This patent discloses that the density of the tinting of the lenses is a function of the angle from the center of the viewer's eye with a maximum absorption being approximately 0.85 and a minimum transmittance being approximately 0.15. The lenses of the present invention have transmittance that could range from 0.25 to 0.03, in other words, the lenses of the present invention are much darker than those in Adrian's patent. Adrian's patent is not intended for use as sunglasses in high luminous environments and does not disclose three distinct areas on the lens for far, intermediate and near vision.
Hutchings (U.S. Pat. No. 2,409,356) discloses a goggle for aviators where brilliant sunlight is encountered such as in flight over bodies of water or deserts, both of which reflect a large amount of solar light. The surface of the lens is coated with a film on upper and lower portions while the central portion is clear. This patent is directed towards the creation of tintings on lenses that have a gradient density (introduction of vignetted sunglasses). This patent also does not disclose three distinct areas on the lens for far, intermediate and near vision, nor does this patent disclose glare reduction from light coming to the viewer from the forward direction. In addition, this patent does not disclose the need to balance the light intensity between the different fields of regard.
Barr (U.S. Pat. No. 1,067,793) discloses automobile driving goggles with a large portion tinted for sunlight and a smaller part which is clear. The purpose of this invention is to enable the viewer to look directly towards oncoming headlights or the sun. This patent does not balance the light from multiple fields of vision, but rather blocks a temporary bright light source in the far field of vision. This patent also does not disclose three distinct areas on the lens for far, intermediate and near vision, nor does this patent disclose glare reduction from light coming to the viewer from the forward direction. In addition, this patent does not disclose the need to balance the light intensity between the different fields of vision.